import sys
sys.setrecursionlimit(10**6)
n=int(input())
w=list(map(int,input().split()))
mid=-(-sum(w)//2)

def dfs(i,le,ri):
    if i==n:
        if le==ri:
            print("possible")
            exit()
        return
    if w[i]+le<=mid:
        dfs(i+1,w[i]+le,ri)
    if w[i]+ri<=mid:
        dfs(i+1,le,w[i]+ri)

dfs(0,0,0)
print('impossible')